南黄海绿潮"沉降区"溶解有机物动态变化及其与绿潮的关系研究OA

Large-scale green tides of Ulva prolifera have been recorded annually in the southern Yellow Sea since 2007.To investigate the potential environmental consequences of the decomposition of massive floating algae dur-ing the decline of green tides,two cruises were performed within the"settlement region"and its adjacent waters in July and September 2023.The dynamics of dissolved organic matter(DOM)were studied by measuring dissolved organic carbon(DOC)concentrations and characterizing DOM fluorescence using excitation–emission matrix spectroscopy(EEMs)combined with parallel factor analysis(PARAFAC).The key findings include:1)DOC con-centrations in the"settlement region"were substantially higher than those in adjacent waters shortly after the de-cline of green tides in July,whereas the concentrations decreased markedly after the complete decline of green tides in September.2)EEMs–PARAFAC analysis showed that DOM exhibited high biological index and low humifica-tion index values in July,indicating a predominance of fresh,labile,and autochthonous organic matter.A significant positive correlation was observed between the fluorescence intensity of protein-like component C2 and the content of the green algal biomarker 28-isofucosterol in surface sediment,highlighting the potential contribution of algal degradation to DOM in seawater.The study highlights that the decomposition of floating green algae after the de-cline of green tides can rapidly alter the concentration of DOC and the composition of DOM in the settlement re-gion,leading to potential ecological consequences that warrant further investigation.